Paul defines God's secret:

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         This mystery is that through the gospel the Gentiles are heirs together with Israel, members together of one body, and sharers together in the promise in Christ Jesus (Eph 3:6).

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          This is a succinct restatement of Eph 2:15-16.  Note the threefold repetition of "together" (other translations are "fellow", "joint").  Paul is laying it on thick -- "The war is over. You Gentiles really belong to the family of God.  You're not the black sheep of the family, nor the half-brother or half-sister.  We are all joint heirs of God."  

           

Paul goes on to say that God gave him the ministry of preaching to Gentiles and declaring the mystery of God's purpose.  Including the Gentiles in His people was only part of God's plan.  The other part was that this unified church, this fellowship of reconciled enemies, would display the wisdom of God even to spiritual powers (Eph 3:10).   To the modern believer this is the greater mystery.  We are not cognizant of these "higher powers,"  nor can we comprehend how God is glorified among them by the behavior of His church.  Given the record of the churches through the ages, He may have regretted this strategy at times.  Yet it shows us the importance God attaches to the "ministry of reconciliation."  

         

Once again, Paul has recast the traditional eschatological expectations.  The conventional program was that Israel would be vindicated in the sight of the nations that had despised her.  Instead, according to Paul, the unification of divided mankind in common allegiance to Jesus vindicates God in the sight of the heavenly powers.  No man is glorified because of his heritage, no man is ashamed of his parentage.  God alone redeems them all, and He Himself is their peace.  It is the reconciliation of Jacob and Esau on a cosmic scale.